Gap plasmon polariton structure for very efficient microscale-to-nanoscale interfacing.

The seamless transition between microscale photonics and nanoscale plasmonics requires overpassing different waveguiding mechanisms and a few orders of magnitude in the lateral dimension. Exploiting gap plasmon-polariton waves both at the microscale and nanoscale with an ultrashort (few micrometers) nonadiabatic tapered gap plasmon waveguide, we show theoretically that very high-power transfer efficiency (approximately 70%) is achieved. The same mechanism may be used to harvest impinging light waves and direct them into a nanohole or slit to exhibit an anomalous transmission without the conventional periodic structures. The interplay of plasmonic and oscillating modes is analyzed.